Structure and Function

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Skeletal System

• Structure and Function

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Functions

• Support body structure and shape
• Protection vital organs surrounded
• Movement/Anchorage of Muscles
• Mineral Storage calcium phosphorus
• Blood Formation
• Bones are the organs of the skeletal system
• Articulations- joints

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Bone Composition

• Collagen chief organic constituent (protein)
• Inorganic Calcium Salts Vitamin D essential for
  absorption
• Osteomalacia- Vit D deficiency leading to
• softening of bone

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Bone Cells

• Osteoblasts bone building and bone forming, bone
  repairing cells in the periosteum
• Osteocytes osteoblast embedded within the bone
  matrix responsible for maturing bone cells
• Osteoclasts cells that cause absorption of bone

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Periosteum

• Dense, fibrous membrane covering bone
  specialized connective tissue covering all bones
  of the body
• Contains blood vessels
• Essential for bone cell
• survival and bone formation

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Connective Tissue

• Ligaments- fibrous band of tissues that connects
  bone to bone
• Tendon- fibrous cords by which muscle is attached
  to bone
• Cartilage- specialized fibrous tissue that acts
  as a shock absorption for joints and is the
  cushion between bones
• Bursa- fluid filled sac b/w tendon or muscle and
  bone acts as a lubricant for movement

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Bone tissue

• Osseuos- (bone) connective tissue made of
  cells, fibers, and extracellular matrix
• Bone marrow- soft, diffuse connective tissue
  responsible for RBC production

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Bones based on Composition

• Cancellous Bone
• Light, Spongy
• Low Stress Areas Where Weight of Bone Would Be a
  Problem
• Found at Ends of Long Bones, Ribs, Sternum, Hips,
  Vertebrae, Cranium

Compact Bone -Very, dense stress-bearing -Carries
nutrients/wastes
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Classification of Bones According to Shape

• Bones are classified according to shape
• Long Bones
• Short Bones
• Flat Bones
• Irregular Bones
• Sesamoid Bones
• There are 206 separate bones in the adult skeleton

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Long Bones

• Extremities
• Femur, tibia, fibula, humerus, ulna, radius,
  clavicle
• Levers
• Epiphysis at the end of
• long bones covered with hyaline cartilage
  for articulating bones cancellous bone

• Diaphysis shaft, covered with periosteum for
  bone growth, repair, nutrition medullary canal
  with yellow and red marrow endosteum lining
  compact bone

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Short Bones

• Cube-shaped
• Allows flexible movement
• Cancellous bone covered by compact bone
• Carpals, tarsals, metacarpals, metatarsals,
  phalanges

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Flat Bones

• Flat Plates
• Protect Vital Organs
• Provide Broad Surface Area for Attachment of
  Muscles
• Cranial Bones, Facial Bones, Scapula, Sternum

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Irregular Bones

• Peculiarly Shaped to Provide Support and
  Protection with Flexibility
• Vertebrae, Ribs, Ear, Hip, Hyoid

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Sesamoid Bones

• Extra Bones Found in Certain Tendons i.e. Patella

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Bone Formation

• Initially collagen fibers secreted by fibroblasts
• Cartilage deposited between the fibers
• Skeleton fully formed by 2nd month of fetal
  development (all cartilage)
• Ossification begins after 8th week of fetal
  development

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Bone Formation

• Childhood and adolescence ossification exceeds
  bone loss
• Early adulthood through middle age ossification
  equals bone loss
• After age 35 bone loss exceeds ossification
• Osteoporosis- a weakening of the bones due to
  inadequate calcium in diet and absorption

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Bone Growth

• Osteoclast- enlarge diameter of medullary cavity
  by eating away the bone of its walls
• Osteoblasts- from periosteum build new bone
  around the outside of the bone (appositional
  growth)
• Endochondral growth- responsible for increase in
  length of bone at epiphyseal plate by the
  diaphysis as result of interstitial cells

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Skull Bone Formation

• Begins as fibrous membrane
• Ossification center in the middle of the membrane
• Ossification begins in the middle and radiates
  out
• Ossification not complete at birth
• Fontanels (soft spots) molding of head during
  birth and allow for brain growth

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Bone Growth

• Grow in length at the epiphyseal line
• Grow in width by addition of bone to the surface
• Controlled by anterior pituitary (GH)

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Bone Markings - Purpose

• Join one bone to another
• Provide a surface for attachment of muscles
• Create an opening for passage of blood vessels
  and nerves
• Use as landmarks

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Bone Marrow - Yellow

• Medullary Cavity of Long Bones
• Fat Storage

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Bone Marrow - Red

• Hematopoietic Tissue
• In cancellous bone in children
• In adults cancellous bone of vertebrae, hips,
  sternum, ribs, cranial bones, proximal ends of
  femur and humerus
• Forms RBCs, platelets, some WBCs and destroys old
  RBCs and some foreign materials
• Inflammation of bone and bone marrow is called
  osteomyelitis

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Axial Skeleton

• Skull (22 Bones)
• Ear (6 Bones) Hyoid
• Vertebral Column (26 Bones)
• Thorax (25 Bones cartilage)

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Skull - Cranium

• Houses and protects the brain
• Frontal forms forehead and orbits of eyes
• Ethmoid forms roof of nasal cavity
• Parietal right left form sides and roof of
  skull
• Temporal right left forms temple, cheek, ear
  openings
• Zygomatic- cheek bones

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Skull

• Occipital back of skull inferior portion has
  foramen magnum (opening for spinal cord) and 2
  condyles to articulate with atlas
• Sphenoid fills space between orbital plates
  depression called sella turcica holds the
  pituitary gland bat shaped

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Skull Bones- Superior View
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Cranial Sutures

• Unite the bones of the cranium
• As the child grow, irregular bands of connective
  tissue ossifies and turns into hard bone
• Abnormalities microcephalus (premature fusion),
  hydrocephalus (delayed fusion ? increases
  intracranial pressure)

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Sutures of Skull

• Coronal Suture between the frontal and parietal
  bones
• Sagittal Suture between right and left parietal
  bones
• Lambdoidal Suture between the parietal and
  occipital bones
• Squamous Suture between temporal and parietal
  bones

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Fontanels

• Fusion of the cranial bones is not complete at
  birth
• Space between the bones remains

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Fontanels

• Anterior (Bregmatic) soft spot, closes at 18
  months
• Posterior (Occipital) triangular, closes at 2
  3 months
• Anteriolateral (Sphenoidal) at 2 temples, closes
  at 2 3 months
• Posterolateral (Mastoidal) 2 behind ears, closes
  at 1 year

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Facial Bones

• Guard and support eyes, ears, nose, mouth
• Nasal bones (2) form bridge of nose
• Vomer forms central nasal septum
• Maxillary (2) upper jaw bone fusion before
  birth forms roof of mouth, walls of nose, floor
  of orbitals
• Mandible lower jaw bone largest bone of face

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Facial bones

• Zygomatic (2) cheek bones
• Lacrimal (2) small bones form medial wall of
  each eye socket
• Palatine (2) forms back roof of mouth and floor
  of nose
• Inferior turbinate (2) forms curved ledge inside
  side wall of nose

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Ear Bones

• Malleus (2) the hammer- passes vibrations from
  eardrum to anvil
• Incus (2) the anvil- passes vibrations from
  hammer to stirrup
• Stapes (2) the stirrup-
• u shaped bone that take
• vibrations from stirrup to
• cochlea smallest bone in body

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Hyoid Bone

• U-shaped bone
• In neck
• At base of tongue and connects to tongue
• Only bone in body that does NOT articulate with
  another bone

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Cranial Sinuses

• Cavities within the cranium
• Resonance chambers for voice
• Decrease weight of skull
• Lined with mucous membrane

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Sinuses

• Frontal sinuses (2) above eyebrows, open into
  nasal cavity
• Ethmoid sinuses (2) between the eyes
• Spenoidal sinus (1) posterior to ethmoidal
  sinus, opens into nasopharynx
• Maxillary sinus (2) on either side of the nose,
  opens into the lateral wall of the nasal cavity

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Vertebral Column Functions

• Supports trunk and neck
• Protects spinal cord
• Multiple joint spaces allow for bending and
  twisting

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Curves

• Allow for resilience and spring for walking
• Thoracic present at birth
• Sacral bow back
• Cervical begins at 3 months when infant first
  begins to lift head
• Lumbar begins when child first walks

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Veterbral Column
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Vertebrae

• 26
• Separated by intervertebral disk to cushion
  joints for movement
• Body thick, disk-shaped anterior portion
• Arch encloses space for spinal cord 3 processes
  for muscle attachment (spinous process dorsally
  directed, 2 transverse processes)

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Vertebral Sections

• Cervical - 7 bones
• Thoracic 12 bones
• Lumbar 5 bones
• Sacral 5 fused bones
• Coccyx (tailbone) 3 4 fused bones
• Kyphosis- hunchback appearance of thoracic region
• Scoliosis- lateral curvature of spine
• Lordosis- curvature of the lumbar spine inward

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Thorax

• 25 bones and cartilage
• Sternum, costal cartilage, ribs
• Walls covered by skin and muscles
• Floor formed by the diaphragm

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Functions

• Protect and support heart and lungs
• Supports bones of pectoral girdle
• Plays leading role in respiration
• Ribs and sternum aid in RBC formation

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Sternum

• Breast bone
• Sword and handle shaped
• Manubrium handle, notched for 1st 7 costal
  cartilages, articulates with acromium end of
  clavicle and 1st rib
• Body blade, notched for 1st 7 costal cartilages
• Xiphoid process tip, attachment site for
  diaphragm

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Costal Cartilage

• Hyaline cartilage
• Connect ribs to sternum in 1 7 and to anterior
  ribs in 8 - 10

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Ribs

• 12 pairs
• Attached posteriorly with vertebrae and
  anteriorly with costal cartilage
• True ribs 1st seven pairs of ribs
• False ribs 8 10
• Floating ribs 11 and 12

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Appendicular Skeleton 126 Bones

• Contains more bones than the axial
  skeleton

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Shoulder Girdle

• Clavicles (2) collar bones most common broken
  bone in children
• Scapulas (2) shoulder blades shoulder bone

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Upper Extremities

• Humerus upper arm
• Radius thumb side of forearm
• Ulna little finger side of forearm
• Carpals (8) wrist bones
• Metacarpals (5) hand bones
• Phalanges/digits (14) finger bones

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Pelvic Girdle

• Os Coxae (2) contains the acetabulum (hip
  socket)
• 3 components ilium, ischium, pubis
• Also, contains the sacrum

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Lower Extremities

• Femur thigh bone (longest and heaviest bone)
• Patella kneecap (largest sesamoid bone in body)
• Tibia shin bone (medial larger bone of lower
  leg)
• Fibula smaller, lateral bone of lower leg
• Tarsals (7) ankle bones talus and calcaneus
• Metatarsals (5) foot bones
• Phalanges (14) toe bones great toe halux

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Conditions

• Gout- chronic joint disease with inflammed and
  painful joints swollen and thickened synovial
  membranes
• Arthritis- a disorder that causes inflammation,
  pain, and stiffness of the joints

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Injuries

• Dislocation
• Subluxation
• Fractures (closed, open, stress and Greenstick)

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The Framework